Adjustable light fixture mounting assembly

ABSTRACT

The components of an adjustable light fixture mounting assembly are secured during adjustment of a light in a lighting system. A knuckle joint with a locking taper secures an upper knuckle half to a lower knuckle half. The locking taper secures the adjustment of the knuckle halves, even if the knuckle screw becomes loosened. In a further embodiment, an O-ring seal between a double locking taper seals the knuckle joint from moisture. A rotating locking clamp secures the lower knuckle half to a nipple with a reverse taper on both the lower knuckle half and the nipple, while allowing rotation of the lower knuckle half with respect to the nipple. Stop pins in the lower knuckle and nipple cooperate with an interior profile of the rotating locking clamp to allow 360 degrees rotation of the lower knuckle half with respect to the nipple.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application is a Continuation of U.S. patent applicationSer. No. 11/041,349, which is a Division of U.S. patent application Ser.No. 10/442,904, filed on May 21, 2003.

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

Not applicable.

REFERENCE TO MICROFICHE APPENDIX

Not applicable.

FIELD OF THE INVENTION

The present invention relates generally to devices for mounting a lightin a lighting system, and more particularly to a light fixture mountingassembly that secures the components of the assembly after adjustment.

BACKGROUND OF THE INVENTION

Outdoor lighting systems use light fixtures that aim a lamp in a desireddirection and are generally intended to keep moisture from theelectrical wiring running through the light fixture. The lamp, such as aspot light or flood light, is aimed to illuminate a particular area.Light fixture mounting assemblies for such applications typicallyinclude adjustable connections that allow the user to aim the light whenthe light fixture is installed, and various seals to keep moisture outof the light fixture.

A knuckle joint between the lamp and a mounting member of the lightfixture mounting assembly is often used to allow limited rotation of thelamp about the knuckle joint. Rotation in this plane is commonlyreferred to as “vertical” adjustment, although this designation is usedonly for convenient discussion, and does not necessarily representrotation of the light in a vertical direction. One type of knuckle jointuses locking teeth or serrations on opposing faces of the knuckle jointhalves. A screw through the axis of the knuckle joint holds the opposinglocking teeth together once the light fixture has been aimed and thescrew has been tightened. Unfortunately, the locking teeth provide onlystep-wise adjustment, and the screw must be loosened to providesufficient clearance to rotate the teeth past each other when aiming thelight fixture. The exact aiming of the light fixture is not apparentuntil the screw holding the knuckle joint halves together has beenre-tightened. Precise aiming of a light fixture with a serrated knucklejoint can involve multiple iterations, and is often done using twopersons.

Other types of light fixtures provide tapers on the mating halves of theknuckle joint. One type of light fixture provides a tapered post on onehalf of the knuckle joint that mates with a tapered hole in the otherhalf of the knuckle joint. The locking screw is tightened to hold thetapered parts together. Loosening the locking screw allows the knucklejoint to smoothly rotate for aiming the light fixture. However, thetapered post has a relatively long taper at a typical taper angle ofabout 7-8 degrees. The long taper results in a thick knuckle joint,which is undesirable when using this type of knuckle joint with smallerlight fixtures.

Another disadvantage of this design is that the wireway for theelectrical wiring goes around the tapered post. Thus, the inner diameterof the wireway through the knuckle joint includes the tapered post.Rotating the knuckle can strain the wiring because the wiring wrapsaround the tapered post.

Another type of light fixture has a tapered structure between the facesof the knuckle halves outside (i.e. beyond the outer diameter) of thewireway. A ridge with a tapered face is formed on one knuckle half, anda groove with a tapered face is formed on the other knuckle half. Thetapered face of the ridge mates with the tapered face of the groove. Thetapered structure provides friction to hold the knuckle halves togetherwhen the locking screw is tight. This light fixture avoids straining thewiring around a thick central post when aiming the light fixture, butthe tapered structure provides relatively little contact area. Thefixture can come out of alignment if the locking screw is notsufficiently tight.

Unfortunately, if the locking screw of any of the above light fixturesloosens, the knuckle joint might rotate if even modest torque isapplied, resulting in the light fixture coming out of alignment. Thelocking screw is particularly likely to loosen in applications where thelight fixture is subject to vibration. For example, light fixtures nearor on a ride at an amusement park, or adjacent to a cobblestone street,experience vibration that can loosen the locking screw. Similarly, somelamps are fairly heavy, and subjecting the light fixture to vibrationmight also provide sufficient torque on the loosened knuckle joint tocause the lamp to come out of alignment. Thus, it is desirable toprovide a lighting fixture that more securely maintains its alignment,and is less susceptible to misalignment if the locking screw loosens.

In addition to allowing adjustment in the vertical direction, many lightfixtures also allow rotational adjustment in the horizontal direction.“Horizontal” adjustment commonly refers to rotating the lamp about anaxis that is orthogonal to the axis of the knuckle joint. Some lightfixtures are horizontally adjusted by loosening a locking nut that holdsthe light mounting assembly to a mounting surface or outlet box,rotating the assembly, and tightening the locking nut. Access to thelocking nut is typically behind the mounting surface or inside theoutlet box, which makes horizontal adjustment difficult. This approachto horizontal adjustment is also trial-and-error, as the installercannot view the aim of the light fixture until after the locking nut hasbeen tightened and the light fixture is secured to the mounting surfaceor outlet box.

Another approach to horizontal adjustment uses a threaded stud that issecured to a mounting surface or outlet box. The stud is rotatablycoupled to a base member of the light fixture. When the light fixture ishorizontally rotated to the desired alignment, a set screw in the basemember is tightened against the stud. However, the set screw has alimited contact area and tends to damage the finish, or even gouge, thesurface of the stud. As with the locking screw of the knuckle joints,the set screw can loosen from a variety of causes, such as vibration. Aslight loosening can allow the light fixture to come out of alignment.If the set screw is sufficiently loosened or removed, such as by acareless maintenance worker, the base member can fall away from thestud. Although the electrical wiring provides some attachment of thelight fixture to its mounting surface, many light fixtures are quiteheavy and the wiring might not hold the light fixture. Dropping thelight fixture could damage the light fixture and cause injuries.Therefore, it is desirable to provide convenient, safe horizontaladjustment of light fixtures.

Horizontal adjustment techniques typically include some sort of devicethat limits rotating the light fixture to about one revolution withrespect to the base. This is a safety requirement for many applications,and avoids undue strain on the wiring that might otherwise result fromrepeatedly wrapping or twisting the wiring. Some light fixtures includea stop member on the stud that interacts with a stop member on the basemember to limit horizontal rotation to less than 360 degrees. However,there is a “dead spot” in the aiming pattern of the light fixture thatoccurs because of the thickness of at least one of the stop members. Itis further desirable to provide horizontal adjustment through at least360 degrees.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A is a simplified side view of a light fixture mounting assemblywith a threaded lower member according to an embodiment of the presentinvention.

FIG. 1B is a simplified cross section of a knuckle joint with aself-locking double taper structure in accordance with an embodiment ofthe present invention.

FIG. 1C is a simplified cross section of a knuckle joint with aself-locking taper structure and O-ring seal according to anotherembodiment of the invention.

FIG. 1D illustrates a portion of FIG. 1B with the groove and ridgespaced apart to better illustrate the first and second groove and ridgesurfaces.

FIG. 2A is a simplified cross section of a light fixture mountingassembly with a clamp according to another embodiment of the presentinvention.

FIG. 2B is a cross section of the clamp taken through section line A-Ain FIG. 2A showing the interior profile of the clamp.

FIG. 2C is a perspective exploded view of the light fixture mountingassembly of FIG. 2A.

FIG. 3 is a cross section of a portion of the light fixture mountingassembly of FIG. 2A illustrating reverse tapers.

DETAILED DESCRIPTION OF THE INVENTION

I. Exemplary Light Fixture Mounting Assemblies

FIG. 1A is a side view of light fixture mounting assembly 10 withthreaded lower member 12 according to an embodiment of the presentinvention. Threaded lower member 12 is attached to mounting surface 14(shown as dashed lines) with locking nut 16. O-ring 17 forms a sealbetween lower member 12 and mounting surface 14. Mounting surface 14could be the cover of an outlet box or a panel, for example.

Electrical wires 18 extend through wireways (not shown in FIG. 1A) inlamp fixture mounting assembly 10 to provide electrical power to a lamp(not shown) that can be attached to body 20 of upper member 22. Body 20can be any of several shapes and configurations depending on the type oflamp that is intended to be used with light fixture mounting assembly10.

Upper member 22 is rotatably attached to lower member 12 through knucklejoint 24. Knuckle joint 24 includes a self-locking taper structure (seeFIGS. 1B, 1C, ref. nums. 28, 28′) that secures upper member 22 to lowermember 12 when locking screw 26 is tightened, and remains secured, evenif locking screw 26 is loosened or removed, until the taper lock isbroken. The taper lock is typically broken by tapping upper member 22with a mallet, or by twisting upper member 22 out of the plane of lowermember 12. In one embodiment, the taper angle of the self-locking taperstructure is less than 7 degrees. In another embodiment, the taper angleis between about 6 degrees and about 3 degrees. In a particularembodiment, the taper angle is about 3 degrees.

FIG. 1B is a simplified cross section of a knuckle joint 24 withself-locking double taper structure 28 in accordance with an embodimentof the present invention. Self-locking double taper structure 28includes a double-tapered ridge 30 on upper member 22 that correspondsto a double-tapered groove 32 in lower member 12. Ridge 30, see FIG. 1D,includes first and second radially spaced apart ridge surfaces 30A, 30Bwhile groove 32 is bounded by first and second radially spaced apartgroove surfaces 32A, 32B. It is generally desirable that the matingfaces of self-locking double taper structure 28 be located as far fromaxis 25 as practical to optimize the locking force(s) obtained fromself-locking double taper structure 28. In an alternative embodiment, adouble-tapered groove is formed in the upper member and thedouble-tapered ridge is formed on the lower member. Each face ofdouble-tapered ridge 30 is formed at a self-locking taper angle ofbetween 3 degrees and 6 degrees (from axis 25 of knuckle joint 24), andeach face is typically, but not necessarily, at the same angle. Theangle shown is exaggerated for purposes of illustration.

When locking screw 26 is tightened, double-tapered ridge 30 is pressedinto double-tapered groove 32 and upper member 22 is locked in positionrelative to lower member 12. Self-locking double taper structure 28holds the angle of upper member 20 to lower member 12 even if lockingscrew 26 is loosened or removed. Alternatively, the self-locking taperstructure may be a single-taper structure or a triple- or othermultiple-taper structure.

However, a double taper structure provides more contact area between thetaper faces than a single taper structure of similar height (measuredalong the axis of rotation of the knuckle joint) and taper angle. Havingmore contact area between the taper faces more securely holds theknuckle joint in the desired configuration after tightening the lockingscrew. In other words, a greater torque would have to be applied toknock the lamp out of alignment. A double taper structure isparticularly desirable in a small light fixture (e.g. a light fixturehaving an outer diameter of lower member 12 of not more than one inch)because a single taper structure with sufficient height to provide thedesired locking force might not fit within the available section withoutunduly constricting the wireway(s).

A wireway 34 in lower member 12 allows the electrical wiring (not shown)to pass around locking screw 26 and into wireway 36 in upper member 22.The electrical wiring does not have to wrap around self-locking doubletaper structure 28, but only the relatively thin locking screw 26,putting less strain on the electrical wiring when knuckle joint 24 isrotated. Having self-locking double taper structure 28 outside ofwireway 35 of knuckle joint 24 also helps to exclude water from enteringthe wireways.

FIG. 1C is a cross section of knuckle joint 24′ with O-ring 38 accordingto another embodiment of the invention. O-ring 38 helps to furtherexclude water from entering the wireways 34, 36, particularly inconjunction with self-locking double taper structure 28′. Self-lockingdouble taper structure 28′ includes double-tapered groove 32′ in lowermember 12. Double-tapered ridge 40, 40′ with taper faces 41, 41′ onupper member 22 includes a slot 42 for O-ring 38 that seals againstdouble-tapered groove 32′ in lower member 12. Alternatively, doubletapered ridge 40, 40′ could be considered two concentric single-taperedridges with an intervening O-ring slot, or the ridge(s) could be formedon the lower member, and the groove in the upper member.

Locking screw 26 is screwed into a blind hole 44. Providing a blindhole, rather than a through hole, prevents moisture from entering theend of locking screw 26. Locking screw 26 provides a clamping forceagainst self-locking double taper structure 28′ that secures knucklejoint 24′ when locking screw 26 is tightened. However, unlike knucklejoints with non-locking tapers, knuckle joint 24′ remains secure, i.e.will not easily rotate, even if locking screw 26 becomes loose, unlessthe taper lock is broken. When installing the light fixture mountingassembly, locking screw 26 is typically tightened just enough to allowrotating upper member 22 about knuckle joint 24′ to aim the light whileholding the position of upper member 22 during aiming. After the lightfixture mounting assembly is adjusted to the desired aim point, lockingscrew 26 is further tightened to lock self-locking double taperstructure 28′.

After self-locking double taper structure 28′ is locked, knuckle joint24′ retains its alignment, even if locking screw 26 becomes loose.Similarly, when self-locking double tapered structure 28′ is locked,knuckle joint 24′ is not easily knocked or shaken out of alignment.Re-alignment of the light fixture mounting assembly is typicallyachieved by loosening locking screw 26 a few turns and tapping uppermember 22 with a mallet to unlock self-locking double taper structure28′. Alternatively, self-locking double taper structure 28′ is unlockedby loosening locking screw 26 and twisting upper member 22 relative tolower member 12 in the plane of axis 25.

FIG. 2A is a simplified cross section of a light fixture mountingassembly 10′ with a clamp 50 according to another embodiment of thepresent invention. Clamp 50 is generally barrel shaped and has reversetapers 52, 52′ on each end that correspond to reverse tapers on lowermember 12′ and nipple 54 (see FIG. 2C, ref. nums. 53, 53′). The reversetapers have inner diameters proximate to the ends of clamp 50 that areless than the inner diameters distal from the ends of clamp 50 (see alsoFIG. 3). Clamp 50 allows lower member 12′ to rotate relative to nipple54 and has a binder screw (see FIGS. 2B and 2C showing binder screw 72and slot 74) that can be tightened to secure the rotational relationshipbetween nipple 54 and lower member 12′. The binder screw can be replacedby other securing elements, such as a C-clamp or a buckle. Reversetapers 52, 52′ hold nipple 54 and lower member 12′ together, even ifclamp 50 is loose or the binder screw is missing.

Light fixture mounting assemblies are made from a variety of materials,such as aluminum, stainless steel, brass, bronze, and fiber-reinforcedpolymer, by a variety of methods, such as machining or casting. Forexample, both aluminum and stainless steel have a “stickier” feel thanbrass or bronze when the knuckle joint is rotated under partialcompression, but not locked. These materials generally provide a greaterlocking force than brass or bronze. However, brass or bronze has a“smoother” feel under partial compression than aluminum or stainlesssteel.

FIG. 2A also shows upper member 22 of light fixture mounting assembly10′ and O-ring 38 of knuckle joint 24′. Nipple 54 is secured to mountingplate 56 with nut 16. Rotation limit pins 60, 62 limit rotation of lowermember 12′ to 360 degrees with respect to nipple 54 in conjunction withan interior profile of clamp 50 (see FIG. 2B, ref. num. 64). Rotationlimit pin 60 is pressed into lower member 12′, and rotation limit pin 62is pressed into nipple 54. In another embodiment, tabs, tangs or otherrotation limiting structure are formed on lower member 12′ and/or nipple54 to operate in conjunction with the interior profile of clamp 50. Inan alternative embodiment, interior profiles are formed in the nippleand in the lower member, and corresponding limit structures, such aslimit pins or tangs, are provided in the clamp.

FIG. 2B is a cross section of clamp 50 taken through section line A-A inFIG. 2A showing interior profile 64 and rotation limit pin 62, which ispressed into nipple 54 (see FIG. 2A). Rotation limit pin 62 allowsrotation of the nipple with respect to clamp 50 from first position 66to second position 68 (shown in dashed lines). Rotation limit pin 62contacts limit portions 70, 70′ of interior profile 64 at first position66 and second position 68, respectively. The limit portions 70, 70′ areconfigured to account for the thickness of rotation limit pin 62 toallow a selected rotation of nipple 54 with respect to clamp 50. In thisembodiment, nipple 54 rotates 180 degrees, and the rotation limit pinpressed into the lower member (see FIG. 2A, ref. nums. 60, 12′) contactsinterior profile 64 of clamp 50 in a similar fashion to allow the lowermember to also rotate a 180 degrees with respect to clamp 50. Thus, thelower member can rotate over 360 degrees with respect to the nipple,eliminating “dead spots” when aiming the light fixture. In anotherembodiment, the lower member rotates 370, or more, degrees with respectto the nipple. Rotation may be limited to less than 360 degrees inalternative embodiments. It is not required that the nipple and lowermember have the same rotation with respect to the clamp. For example, athicker pin could be used in one half, and a thinner pin in the other,or the interior profile of the clamp could present different limitportions to each pin.

Binder screw 72 tightens clamp 50 about the nipple and lower member byclosing slot 74, which runs longitudinally along clamp 50. Binder screw72 is transverse to slot 74 and pulls slot 74 together when tightened.Clamp 50 is attached to the nipple and lower member by substantiallyloosening or removing binder screw 72 and spreading slot 74, such aswith a screw driver, to allow the ends of clamp 50, which are reversetapered, to slip over the corresponding reverse-tapered ends of thenipple and lower member.

FIG. 2C is a perspective exploded view of the light fixture mountingassembly 10′ of FIG. 2A. Nipple 54 is secured to mounting plate 56 orsimilar mounting surface with nut 58. O-ring 76 seals nipple 54 againstmounting plate 56. Another O-ring 78 seals the wireway in nipple 54 withlower member 12′, while allowing rotation of nipple 54 with respect tolower member 12′. Pin 62 is pressed into nipple 54 and operates inconjunction with an interior profile (see FIG. 2B, ref. num. 64) ofclamp 50 to limit rotation of nipple 54 with respect to clamp 50. Pin 60is pressed into lower member 12′ and also operates in conjunction withthe interior profile of the clamp to limit rotation of lower member 12′with respect to clamp 50.

A reverse taper 53′ is formed on nipple 54 to mate with thecorresponding reverse taper (see FIG. 2A, ref. num. 52′) in clamp 50.Similarly, a reverse taper 53 is formed on the end of lower member 12′to mate with corresponding reverse taper 52 in clamp 50. A tool, such asa screwdriver, is used to spread slot 74 open to allow insertion of thereverse taper 53′ of nipple 54 and the reverse taper 53 of lower member12′ into the opposite ends of clamp 50. In a particular embodiment, thereverse tapers 52, 52′ on each end of the clamp are the same, i.e.either end of the clamp will mate with either the nipple 54 or with thelower member 12′. When the tool is removed from slot 74 clamp 50 retainsnipple 54 and lower member 12′ (and associated parts, such as uppermember 22 and any light attached to upper member 22), even if binderscrew 72 is loose or missing. This is not only convenient wheninstalling the light fixture mounting assembly, but also an importantsafety feature that prevents potentially heavy parts of the lightfixture from in advertently falling. Lower member 12′ can be rotated atleast 360 degrees with respect to nipple 54 for aligning the lightfixture, and secured by tightening binder screw 72, which provides acircumferential clamping force about the reverse tapers, drawing thenipple and lower member together with the reverse tapers and securingthe alignment of the lower member with respect to the nipple withoutsubstantially marring the finish or surface of the lower member, nipple,or clamp. The circumferential clamping also provides greater securingforce than typically achieved with a simple set-screw, and slightelastic deformation of the clamp when the binder screw is tightenedprovides tension on the binder screw to resist loosening, such as fromvibration.

FIG. 3 is a simplified cross section of clamp 50 and associatedcomponents illustrating reverse tapers, which are exaggerated forpurposes of illustration. Lower member 12′ is coupled to clamp 50 withreverse taper 52 and nipple 54 is coupled to clamp 50 with reverse taper52′. Wireway 84 extends through nipple 54, which is sealed to lowermember 12′ with O-ring 78.

Modification and variation can be made to be disclosed embodimentswithout departing from the subject of the invention as described herein.Any and all patents, patent applications and printed publicationsreferred to above are incorporated by reference.

1. A light fixture mounting assembly comprising: a first member; asecond member rotatably coupled to the first member; a nipple; a chosenone of the nipple and the second member configured to be attached to amounting surface; the nipple having an outer, circumferentiallyextending nipple mounting surface; the second member having an outer,circumferentially extending second member mounting surface; a clamphaving first and second inner, circumferentially extending clampmounting surfaces rotatably engaging the nipple and second membermounting surfaces; and the clamp being circumferentially tightenableonto the nipple and the second member to rotationally secure the secondmember with respect to the nipple.
 2. A light fixture mounting assemblycomprising: a first member; a second member rotatably coupled to thefirst member; a nipple; a chosen one of the nipple and the second memberconfigured to be attached to a mounting surface; the nipple having anouter, circumferentially extending nipple mounting surface; the secondmember having an outer, circumferentially extending second membermounting surface; a clamp having first and second inner,circumferentially extending clamp mounting surfaces rotatably engagingthe nipple and second member mounting surfaces; the clamp beingrotatably coupled to the nipple with a first reverse taper and rotatablycoupled to the second member with a second reverse taper; and means forcircumferentially tightening the clamp onto the nipple and the secondmember to rotationally secure the second member with respect to thenipple.
 3. The light fixture mounting assembly according to claim 1wherein: the first and second inner, circularly extending clamp mountingsurfaces rotatably engage the nipple and second member mounting surfaceswith first and second reverse tapers, respectively; and the first andsecond reverse tapers bias the nipple and second member towards oneanother.